The books is about a sixth grader with Epilepsy (Chance). On the last day of school, a number of high school students (including his brother) are taken/drafted by the military (the military needs older teenagers to conduct certain experiments). Chance has been looking forward to the summer, because it's a time when his family can be together and relax (the stress of school makes his seizures worse). Obviously, when his brother is taken by the military, the intended summer is stripped away. While Chance and his family try to figure out what's going on, Chance starts "seeing" a man hanging out by his treehouse in the back yard. It turns out, this "man" is a creature from another realm/dimension called an omnituen (means all-seeing).